When the NFL agreed in 2012 to donate tens of millions of dollars to concussion research overseen by the National Institutes of Health, it was widely seen as a positive turning point in football’s long history of playing down the long-term effects of brain injuries on players. At the time, the league said that it would have no influence over how the money was used.

But the league and its head, neck and spine committee worked to improperly influence the government research, trying to steer the study toward a doctor with ties to the league, according to a study conducted and released by a congressional committee Monday.

“Our investigation has shown that while the NFL had been publicly proclaiming its role as funder and accelerator of important research, it was privately attempting to influence that research,” the study concluded. “The NFL attempted to use its ‘unrestricted gift’ as leverage to steer funding away from one of its critics.”

The NFL, in a statement, said it rejected the accusations laid out in the study, which was conducted by Democratic members of the House Committee on Energy and Commerce. “There is no dispute that there were concerns raised about both the nature of the study in question and possible conflicts of interest,” the league said. “These concerns were raised for review and consideration through the appropriate channels.”

It is the latest in a long history of instances in which the NFL has been found to mismanage concussion research, dating to the league’s first exploration of the crisis when it used deeply flawed data to produce a series of studies.

In this case, some of the characters are the same, including Dr. Elliot Pellman, who led the league’s concussion committee for years before he was discredited for his questionable credentials and his role as a longtime denier of the effects of concussions on players.

Others are more recent members of the league’s concussion committee, like Dr. Richard Ellenbogen, co-chairman of the league’s committee on brain injuries. According to the congressional study, he bid on the research grant, then directly lobbied the National Institutes of Health to discredit the work of Dr. Robert Stern, the Boston University neurologist to whom it was awarded.

In the end, the NIH did not receive the $16 million from the NFL that it expected for Stern’s research, the study found. And Rep. Frank Pallone Jr. of New Jersey, who oversaw the study, accused the NFL of trying to influence research that it promised to support without interference.

“The NFL’s troublesome interactions with the NIH fit a longstanding pattern of attempts to influence scientific understanding of degenerative diseases and sports-related head trauma,” Pallone said in a statement. “The NFL must recognize the importance of this ongoing, impartial research, and live up to its funding commitments to NIH.”

Results of the study were first reported by ESPN. It also criticized the Foundation for the National Institutes of Health, or FNIH, a nonprofit intermediary between the NIH and its private and public donors, for not “adequately” buffering the relationship between the NIH and the NFL.

The 91-page study said the NFL funded the first four research projects by the NIH, but it made an issue over a proposed fifth. The NIH recommended a study to characterize chronic traumatic encephalopathy, or CTE, in high-risk adults over the course of three to five years. CTE, a degenerative brain disease, is caused by repeated blows to the head. For now, it can only be diagnosed posthumously, and has been discovered in roughly 100 deceased former NFL players.

A year ago, the NIH’s National Institute of Neurological Disorders and Stroke concluded a peer-review grant process and recommended that Stern’s proposal be chosen. The research was expected to cost $17.5 million, with $16.3 million of it funded by the NFL

Stern, a professor of neurology and neurosurgery, is director of clinical research for Boston University’s CTE Center, a leader in the budding research of the disease. It was the work conducted at Boston University, along with a few others, that propelled the issue of concussions into the national consciousness over the past decade.

The NFL long had an uneasy relationship with Boston University, as the league denied the effects of concussions for years, even as evidence and public pressure grew. Without admitting wrongdoing, it settled a class-action lawsuit brought by former players for about $1 billion. At a congressional hearing this year, Jeff Miller, the NFL’s senior vice president for health and safety, admitted to a link between football and brain diseases like CTE.

The congressional study released Monday said the NFL tried to pressure the NIH into steering the grant away from Stern.

“There are many of us who have significant concerns re BU and their ability to be unbiased and collaborative,” Pellman, who spent 13 years as chairman of the NFL’s Mild Traumatic Brain Injury Committee from 1994 to 2007, wrote in an email to Maria Freire, president and executive director of the FNIH

Pellman said several others with ties to the NFL were concerned by the choice, too. Among them, he wrote, were Ellenbogen and Betsy Nabel, the NFL’s chief medical officer. They and others also took part in a conference call with NIH officials, and some followed up with calls and emails to discredit the Stern proposal.

The NIH moved forward with Stern’s proposal. The National Institute of Neurological Disorders and Stroke reaffirmed in a September meeting that Stern had no conflict of interest and that his proposal received the highest score in the grant application review.

But over the next several months, the NFL’s Miller and the FNIH’s Freire debated the league’s commitment to funding the research. The league ultimately said it would provide $2 million for the first year of the study. The NIH declined the offer and said it would rather use its own money and reserve the $16 million for future research.

The congressional study blamed the FNIH for “failing to effectively fulfill” its role by allowing league officials to directly lobby with the NIH and not holding the league to its financial commitment.

“A series of misunderstandings and disputes might have been avoided had FNIH reminded the NFL of its obligation to fund the study” under the original agreement years before, the study concluded.

The study by Democratic members of the House Committee on Energy and Commerce began in December, after reports that the NFL was backing out of its promises to fund concussion research objectively.